In a TOF sensor, a light source emits light towards a scene. A time-of-flight detection pixel, or TOF pixel, of the sensor receives the light reflected by a point of the scene conjugate with this pixel. The measurement of the time of flight, that is, of the time taken by the light to travel from the light source to the point of the scene of which the pixel is conjugate, and from this point to the pixel, enables to calculate the distance separating the pixel from this point.
In the case where a three-dimensional image of a scene is desired to be obtained, the TOF sensor comprises an array of TOF pixels to measure the distance separating each pixel from the point of the scene conjugate with this pixel. This provides a mapping of the distances separating the sensor from the different points of the scene conjugate with the pixels, and a three-dimensional image of the scene can then be reconstructed from this distance mapping. However, current TOF pixels have relatively large dimensions. For example, a TOF pixel comprising a SPAD-type photodiode (“Single Photon Avalanche Diode”) may have a surface area in the order of 30 μm by 30 μm.
It would thus be desirable to have a TOF pixel overcoming at least some of the disadvantages of existing TOF pixels, particularly a TOF pixel having a surface area smaller than 10 μm by 10 μm, preferably smaller than 5 μm by 5 μm.